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Hughes / Boeing: HS-702 / BSS-702, HS-GEM / BSS-GEM (Geomobile)

Evolved from the popular, proven 601 and 601HP (high-power)
spacecraft, the body-stabilized Boeing 702 is the world leader in capacity, performance
and cost-efficiency.

The Boeing 702 design is directly responsive to what customers said they wanted in a
communications satellite, beginning with lower cost and including the high reliability for
which the company is renowned. For maximum customer value and producibility at minimum
total cost, the Boeing 702 offers a broad spectrum of modularity. A primary example is
payload/bus integration. After the payload is tailored to customer specifications, the
payload module mounts to the common bus module at only four locations and with only six
electrical connectors. This design simplicity confers major advantages. First,
nonrecurring program costs are reduced, because the bus does not need to be changed for
every payload, and payloads can be freely tailored without affecting the bus. Second, the
design permits significantly faster parallel bus and payload processing. This leads to the
third advantage: a short production schedule.

Further efficiency derives from the 702's advanced xenon ion propulsion system
(XIPS), which was pioneered by BSS and is produced today by Boeing Electron Dynamic
Devices, Inc. XIPS is 10 times more efficient than conventional liquid fuel systems. Four
25-cm thrusters provide economical stationkeeping, needing only 5 kg of fuel per year
– a fraction of what bipropellant or arcjet systems consume. Using XIPS for final
orbit insertion conserves even more mass as compared to using an on-board liquid apogee
engine. Customers can apply the weight savings to substantially increase the
revenue-generating payload at small marginal cost, to prolong service life, or to change
to a less expensive launch vehicle (when cost is based on satellite mass). For even more
versatility, the Boeing 702 also incorporates a bipropellant propulsion system, which can
lift the satellite into final orbit after separation from the launch vehicle.

Innovation extends to the Boeing 702 power systems as well. The Boeing 702 offers a
range of power up to 18 kW. Dual and triple-junction gallium arsenide solar cells enable
such high power levels. Spectrolab, Inc. a Boeing subsidiary, developed the cells.

The first version of the 702 used solar arrays with concentrators. These concentrators
tended to early fogging, as due to an inherent design flaw the outgassing of the solar
cells was higher than expected. This fogging lead to much reduced lifetime. The flaw was
corrected in later versions with higher power triple-junction gallium arsenide solar
cells.

The Boeing 702 separates the bus and payload thermal environments and substantially
enlarged the heat radiators to achieve a cooler, more stable thermal environment for both
bus and payload. This increases unit reliability over service life. Deployable radiators
use flexible heat pipes, which increase packageable radiator area. Further thermal control
occurs through passive primary rejection via heat pipes.

The Boeing GEO-Mobile satellite system features a 12.25-meter deployable antenna, and
onboard digital signal processing and beamforming. It is a
mobile-communications-supporting satellite system that integrates a Boeing
geosynchronous-orbit satellite with a ground segment and a user terminal segment.

In 1997, Hughes Space and Communications Company, now Boeing Satellite Systems,
received a nearly $1 billion contract for Thuraya, a system consisting of two GEO-Mobile
satellites that will serve the Middle East, North and Central Africa, Europe, Central Asia
and the Indian subcontinent. It is the largest satellite communications project in the
region and will serve nearly 1.8 billion people. The first Thuraya satellite was launched
in October 2000. Thuraya-2 was launched in June 2003.

In 2008 Boeing introduced the midsized 702MP. The MP is only slight less heavy than the HP—about 12,500 lb.—but has mid-range power at 6-12 kW, although Intelsat has launched it with hosted payloads. Intelsat remains the MP’s only customer.

In 2012, Boeing introduced the 702SP, the smallest member of the family, which has been under development for the past two years and completes a geostationary series with power ranges of 3-18 kW. With the 702SP, Boeing is offering a van-sized spacecraft—15 ft. high and 7 ft. wide—that weighs 4,000 lb. at launch. Unlike its two larger family members, it will use an all-electric station-keeping propulsion system. The MP and HP rely on a mixed use of chemical propellants and electric propulsion.

Failures:

Following failures of 702 models have occured:

Anik F1: - degradation of solar concentrators - long term power loss

Galaxy 11: - degradation of solar concentrators - long term power loss

PAS 1R: - degradation of solar concentrators - long term power loss

Thuraya 1: - degradation of solar concentrators - long term power loss